java - 使我的处理器达到峰值的方法

Question

这个问题已经有答案了:

已关闭 14 年前。

Possible Duplicate:
How do I start optimising my Java code? - CPU is at 100%

我有一个 isReset() 方法，它疯狂执行，我将其定义为

   public boolean isReset() { return reset; 
   }

在另一个类(class)。下面的类是唯一使用此代码的类。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.IOException;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.KeyStroke;
import javax.swing.border.BevelBorder;
import javax.swing.border.SoftBevelBorder;


// TimerQueue

public class SkaTest {
   public static final int WIDTH = 500;
   public static final int HEIGHT = 500;
   public static final int CANVAS_X = 100;
   public static final int CANVAS_Y = 100;
   public static final int CANVAS_FRAME_WIDTH = WIDTH+100;
   public static final int CANVAS_FRAME_HEIGHT = HEIGHT + 100;
   public static final int EXEC_WIDTH = 550;
   public static final int EXEC_HEIGHT = 400;

   static VizDSList dsList = new VizDSList();
   static SkaCanvas canvas = new SkaCanvas(dsList);
   static JFrame canvasFrame = new JFrame("Data Structure Canvas");
   static JMenuBar menuBar = new JMenuBar();
   static JMenu algorithmMenu = new JMenu("Algorithm");
   static JMenu dsMenu = new JMenu("Create");
   static JMenu helpMenu = new JMenu ("Help");
   static JLabel status = new JLabel(" ");   

   static SkaProgram[] alg;
   static JFrame execFrame[];
   static SkaExecutionPanel execPanel[];


   public static void setupFrames(int nAlgs) {
      int i; 

      for (i=0; i < nAlgs; i++) {
         // execFrame[i] = new JFrame("Execution Control Panel "+(i+1));
         execFrame[i] = new JFrame();
         execPanel[i] = new SkaExecutionPanel(execFrame[i]);
      }

      canvas.setMinimumSize(new Dimension(WIDTH, HEIGHT));
      canvasFrame.setSize(CANVAS_FRAME_WIDTH, CANVAS_FRAME_WIDTH);
      canvasFrame.getContentPane().setLayout(new BorderLayout(10,7));
      // canvasFrame.getContentPane().setPreferredSize(new Dimension(WIDTH, HEIGHT));
      canvasFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
      // canvas.setMinimumSize(new Dimension(WIDTH, HEIGHT));

      for (i=0; i < nAlgs; i++) {
         execFrame[i].setSize(EXEC_WIDTH, EXEC_HEIGHT);
         // execFrame[i].getContentPane().setLayout(new BorderLayout(10,7));
         execFrame[i].addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
               System.exit(0);
            }
         });
         execPanel[i].setBorder(new SoftBevelBorder(BevelBorder.RAISED));
         // execFrame[i].setContentPane(execPanel[i]);
         execFrame[i].getContentPane().add("Center", execPanel[i]);
         // execFrame[i].setLocation(CANVAS_X +CANVAS_FRAME_WIDTH, CANVAS_Y + i*EXEC_HEIGHT);
         execFrame[i].setLocation(CANVAS_X +CANVAS_FRAME_WIDTH + i*30, CANVAS_Y + i*50);
      }

      canvas.setBorder(new SoftBevelBorder(BevelBorder.RAISED));
      canvasFrame.getContentPane().add("Center", new JScrollPane(canvas) );
      // canvasFrame.getContentPane().add("Center", new JScrollPane(canvas, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS) );
      canvasFrame.getContentPane().add("South", status);
      canvasFrame.setLocation(CANVAS_X, CANVAS_Y);

      JMenu fileMenu = new JMenu("File");
      JMenuItem quitItem = new JMenuItem("Quit");
      //TODO Add quit listener
      quitItem.addActionListener(new ActionListener ()
      {


        public void actionPerformed(ActionEvent arg0) {
            //System.exit(0);

            int again = JOptionPane.showConfirmDialog(null, "Are you sure you want to exit system", "Exiting", JOptionPane.YES_NO_OPTION);
            if (again == JOptionPane.YES_OPTION)
            {
                System.exit(0);
            }


        }

      }
      );
      fileMenu.add(quitItem);
      menuBar.add(fileMenu);
      menuBar.add(algorithmMenu);
     // menuBar.add(dsMenu);
      menuBar.add(helpMenu);
      JMenuItem help = new JMenuItem ("Help Contents");
      //help.setMnemonic(KeyEvent.VK_H);
      //TODO Fix this method
      help.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F1, ActionEvent.CTRL_MASK));
      help.addActionListener(new ActionListener()
      {
/*
        @Override
        public void actionPerformed(ActionEvent arg0) {
            JOptionPane.showMessageDialog(null, "Alot of the functionality have not yet been included in this version\nCurrently working on the automation features now!", "SKA 0.2 Beta", JOptionPane.WARNING_MESSAGE);

        }
*/

        public void actionPerformed(ActionEvent arg0) {
            try {
                Runtime.getRuntime().exec("hh.exe C:/ska.chm");
            } catch (IOException e) {
                e.printStackTrace();
                JOptionPane.showMessageDialog(null, "File not found", "Error", JOptionPane.ERROR_MESSAGE);
            }


        }

      });
      JMenuItem about = new JMenuItem ("About SKA");
      about.addActionListener(new ActionListener(){


        public void actionPerformed(ActionEvent arg0) {
        JOptionPane.showMessageDialog(null, "SKA Version 0.1 Beta");

        }
    });
      helpMenu.add(help);
      helpMenu.add(about);
      canvasFrame.setJMenuBar(menuBar);
   }

   /** The create menu item  */
   public static void createProgram(int i) {
      JMenuItem algItem;
      switch (i) {
      case 0 :
          alg[0] = new RedBlackValidate(canvas, execPanel[0]);
          execFrame[0].setTitle("Validate Algorithm");
          System.out.println("Validate Algorithm");
          algItem = new JMenuItem("Validate Algorithm");
          algorithmMenu.add(algItem);
          break;
      default:
         break;         
      }
   }


   public static void main(String args[]) {
      int i, nAlgs = 1; //nAlgs = 7;

      alg = new SkaProgram[nAlgs];
      execPanel = new SkaExecutionPanel[nAlgs];
      execFrame = new JFrame[nAlgs];

      // canvas.setDebugGraphicsOptions(DebugGraphics.BUFFERED_OPTION);
      setupFrames(nAlgs);
      canvasFrame.setVisible(true);


      for (i=0; i < alg.length; i++) {
         createProgram(i);
         execFrame[i].setVisible(true);
         alg[i].start();
         alg[i].displayAlgorithm();
      }

      while (true) {
         for (i=0; i < alg.length; i++) 
            if (execPanel[i].isReset()) {
               alg[i].terminate();
               createProgram(i);
               alg[i].start();
               execPanel[i].unreset();
            }         
      }
   }
}  // End class SkaTest

Answer 1

isReset 没有任何问题，但是这个循环不会一遍又一遍地调用它(一遍又一遍......)吗？

 while (true) {
     for (i=0; i < alg.length; i++) 
        if (execPanel[i].isReset()) {
           alg[i].terminate();
           createProgram(i);
           alg[i].start();
           execPanel[i].unreset();
        }         
  }

如果不出意外，您可以在其中添加一个 Thread.yield() 来强制线程定期放弃其时间片，这样它就不会占用 CPU。

更好的办法是放弃轮询，而使用基于监听器的方法。允许 execPanel 在重置时通知监听器，而不是让一个循环反复询问它们是否已重置。这段代码相当于“我们到了吗？我们到了吗？我们到了吗？”

您可能还会看到名为 observers 的监听器。如果您四处寻找有关此的更多信息 design pattern使用这两个术语会出现很多有用的信息。

示例

以下是您可以如何重写代码以使用监听器概念。对于这段代码中的任何错误，我深表歉意，我还没有编译它。尽管我的代码中可能存在任何错误，但希望这些想法是清晰的。

如果代码立即没有意义，请查看我上面的链接。或者你可以玩一下 EventListeners ，当您进行 Swing GUI 编程时，您将一直使用它。

public class SkaExecutionPanel {
    // Anybody who wants to be told when a panel is reset will implement
    // this interface and call addListener().
    public interface Listener {
        void panelReset(SkaExecutionPanel panel);
    }

    // Each panel needs to maintain an internal list of listeners.
    private List<Listener> listeners = new ArrayList<Listener>();

    public void addListener(Listener listener) {
        listeners.add(listener);
    }

    public void removeListener(Listener listener) {
        listeners.remove(listener);
    }

    public void reset() {
        /* Do your thing. */

        // When something happens that the listeners will care about, such as a
        // call to reset() in this case, you iterate through the list and tell
        // each one what's happened.
        for (Listener listener: listeners) {
            listener.panelReset(this);
        }
    }
}

public class SkaTest {
    public static void main(String args[]) {
        /* Snippety snip. */

        for (i=0; i < alg.length; i++) {
            // Here we need to tell the execPanels that we want to do something
            // whenever somebody calls reset() on them. We will add a listener
            // to each panel that does the terminate/createProgram/start dance.
            // This way we don't have to ask the panels when they are reset; 
            // instead they will tell us when that happens.
            execPanel[i].addListener(new SkaExecutionPanel.Listener() {
                final int index = i;

                public void panelReset(SkaExecutionPanel panel) {
                    alg[index].terminate();
                    createProgram(index);
                    alg[index].start();
                    execPanel[index].unreset();
                }
            });
        }
    }
}